From 50f171d5c86a21727ff6387acf694ba44281d030 Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Thu, 11 Feb 2016 15:48:46 -0500
Subject: [PATCH] which command

---
 builtins.cpp |  6 ++++++
 builtins.h   |  1 +
 command.cpp  | 30 ++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/builtins.cpp b/builtins.cpp
index 4662f5f..7365d1c 100644
--- a/builtins.cpp
+++ b/builtins.cpp
@@ -12,6 +12,9 @@
 #include <cstdio>
 #include <cctype>
 
+#include "cxx/string_splitter.h"
+#include "cxx/filesystem.h"
+
 //MAXPATHLEN
 #include <sys/param.h>
 
@@ -21,6 +24,9 @@ namespace ToolBox {
 	std::string UnixToMac(const std::string path);
 }
 
+
+namespace fs = filesystem;
+
 namespace {
 
 /*
diff --git a/builtins.h b/builtins.h
index d7d91c7..3620fa2 100644
--- a/builtins.h
+++ b/builtins.h
@@ -16,6 +16,7 @@ int builtin_set(Environment &e, const std::vector<std::string> &, const fdmask &
 int builtin_unset(Environment &e, const std::vector<std::string> &, const fdmask &);
 int builtin_export(Environment &e, const std::vector<std::string> &, const fdmask &);
 int builtin_unexport(Environment &e, const std::vector<std::string> &, const fdmask &);
+int builtin_which(Environment &e, const std::vector<std::string> &, const fdmask &);
 
 int builtin_evaluate(Environment &e, std::vector<token> &&, const fdmask &);
 
diff --git a/command.cpp b/command.cpp
index bbc1c8a..d5f6b51 100644
--- a/command.cpp
+++ b/command.cpp
@@ -12,6 +12,8 @@
 #include <cerrno>
 #include <cstdlib>
 
+#include "cxx/filesystem.h"
+#include "cxx/string_splitter.h"
 
 #include <unistd.h>
 #include <sys/wait.h>
@@ -19,6 +21,34 @@
 
 extern volatile int control_c;
 
+namespace fs = filesystem;
+extern fs::path mpw_path();
+
+namespace ToolBox {
+	std::string MacToUnix(const std::string path);
+	std::string UnixToMac(const std::string path);
+}
+
+fs::path which(const Environment &env, const std::string &name) {
+	std::error_code ec;
+
+	if (name.find_first_of("/:") != name.npos) {
+		// canonical?
+		fs::path p(name);
+		if (fs::exists(p, ec)) return name;
+		return "";
+	}
+
+	std::string s = env.get("commands");
+	for (string_splitter ss(s, ','); ss; ++ss) {
+		fs::path p(ToolBox::MacToUnix(*ss));
+		p /= name;
+		if (fs::exists(p, ec)) return p;
+	}
+
+	// error..
+	return "";
+}
 
 void launch_mpw(const Environment &env, const std::vector<std::string> &argv, const fdmask &fds) {